There are cases where securities and the like are provided with an optical variable image device in order to counteract fraud such as counterfeiting. An optical variable image device is a device with which different images are observable from different observation directions. For example, a hologram is one type of optical variable image device.
An inspector observes an optical variable image device provided on a security to be inspected from a plurality of predetermined observation directions and checks whether each of the viewed images is correct. If the individual images are correct, the inspector determines that the optical variable image device is genuine, and accordingly the security provided with that optical variable image device is also genuine. On the other hand, if at least one of the images is not correct, the inspector can determine that the optical variable image device is a counterfeit, and accordingly the security provided with that optical variable image device is also a counterfeit.
As described above, optical variable image devices have a property of allowing different images to be viewed from different observation directions, and can therefore effectively prevent counterfeiting by copying and other techniques in which light is irradiated from only one direction. However, this property of the optical variable image devices also makes it difficult to process an image observed from an optical variable image device as machine-readable information. For this reason, there are cases where it is difficult to perform authenticity determination of an optical variable image device by image processing of an image that is optically read from the optical variable image device.